Rotational casting is a method of producing fascia type parts or other parts which require a thin skin type portion. For instance, the rotational casting process is used to produce instrument panel fascias in the automotive industry, but is also useful whenever a fascia type part which has a skin type layer having an even thickness and a contoured surface is desired to be produced.
Generally a rotational cast process consists of the use of a mold having an inner cavity which cavity has molding surfaces which are contoured to correspond to that of a finished part. Commonly the mold is configured in two halves each of which has a molding surface for a separate fascia part. Plastic powder molding material corresponding to the desired material used in the final part is introduced into the cavity formed by the two halves of the mold. The mold is then placed into an oven and then heated to a temperature which will induce flashing or melting on the molding surfaces in the plastic material used. To ensure an even thickness the mold is agitated or rotated to evenly distribute the plastic powder along the entire mold surfaces. Thus, as the plastic powder touches the heated mold surfaces it instantly flashes or melts and creates a uniform coating over the mold surfaces which is insured by the rotation and/or agitation of the mold. Subsequently the mold is allowed to cool and it then must be removed from the assembly, trimmed to its proper dimensions and may then be used.
Due to the nature of this process in that the two halves must be joined together and sealed so that the powder will not escape and will be distributed throughout the surfaces during the rotating and agitating process, the mold cavities are generally produced with extraneous or non-critical areas which are there to provide a joining of the two molds in the cavity or for other reasons other than to provide a molding surface for the final part. These extraneous or non-critical surfaces while necessary to the molding process create extra surfaces which cause unwanted flashing material in the finished product in that they are also heated during the casting process and subsequently powdered material coats these surfaces along with the critical molding surfaces. This creates undesirable extra material in the finished part which must be removed or trimmed from the part prior to installing the part or using the part in its finished form.
Thus, while the finished part obtained from this process creates a suitable part the process necessitates the step of trimming the part to remove the excess material which is somewhat time consuming and also creates extra material usage because of the wasted material which must be trimmed before shipping or using the final part. These extra steps are undesirable in that excess labor and product costs are consumed by such a procedure. Therefore, it is desirable to solve this problem of wasted labor and material in the rotational casting art to provide cost savings in production and also an improved finished product.